"It offers essential support not only to air power operations but also to every aspect of joint capability across defence, and in concert with our allies."

Britain's allies in the US played an important role in the Airseeker's development, with L-3 Mission Integration in Greenville, Texas, having converted three KC-135 air-air refuelling aircraft to RC-135 standard.

The US government also provided ground infrastructure, training of personnel and ground support systems.

The third aircraft arrived at RAF Waddington, in Lincolnshire, last year but is now deployable in support of national and coalition operations.